Need help with diagnosis

[Unsane]

Hi All! New member, new bike, new problems...

I have an issue with my 2004 F and was hoping someone could give me advice on the possible/probably causes – if there is common cause of the symptom I would like to tackle that first before going too deep...

When cruising or trying to maneuver at low speeds, trying to apply very small amounts throttle or when coming back on the throttle after full release, the engine seems to kick in the frame as the power comes back on– almost like it has a busted engine mount or massive backlash inside the gearbox. This happens almost every time unless you are ultra-slow & ultra-smooth with reapplication of the throttle

Also when trying to crawl along at very low speed or when pulling out of a corner under 3000rpm in say 3rd gear the engine can shakes the shaZam! out of the bike like its laboring heavily... but once it gets over 3 grand it seems fine. Do these engines normally bog down like this at low revs under a bit of load?

I have only owned the bike for a fortnight so I am still getting accustomed to its "personality". If it makes any difference, the previous owner had the sprockets changed recently but I don't think the chain was done at the same time – could this be a possible cause? The bike as 34,000km and seems to have been serviced and treated well...

Any ideas before I start pulling the bike to pieces would be greatly appreciated!

Cam

[adidasguy]

That backlash sounds like a chain problem. Is it properly tightened? Lubed? Rear wheel straight?
When sprockets are changed, the chain should also be changed. They wear down together.
34,000 km on one chain is a bit on the high side.
Chain may not have been replaced because the factory chain has no key link. You either cut the chain or remove the rear swing arm.

[scratch]

Under 3000rpm is considered lugging the motor.  Try to keep the rpm's up.  Around 4000rpm

[adidasguy]

3rd gear 3k rpm could be a bit sluggish especially if up hill. What will happen in the coming weeks is you will find the personality of your bike and what RPM's , gears and speeds make it happy. Things also depend on how well tuned your bike is.

Suzi, my 2009 runs great at 2k - 4k RPM. She's real happy at 3k.
Junior, my 1992, likes things a little higher. He's happiest around 4k - 5k RPM. Gets a little cranky when you get down below 3k RPM.

So I've learned my 2 bike's personalities and shift & drive differently.

Do check on your chain. Cardinal rule is to change chain and sprockets together because they wear together. Lose and worn chain could be wreaking havoc with the new sprockets. Rear wheel not straight means chain is going over rear sprocket at an angle causing more problems. These problems may only manifest themselves at certain speeds.

[the mole]

After replacing the chain it would be worthwhile to clean the carbs, start by just opening the drains and flushing them through a little, that may shift crud in the carbs and only takes a few minutes.

[Unsane]

Thanks for the advice guys!

Coming from a cyclist background, I have religiously replaced the front chain rings and rear cassette whenever the chain was renewed so I kinda figured it was the same for motorcycles... I was a little suspicious when the previous owner told me ONLY the sprockets had been changed. I did have to tension the chain when I first picked it up and was very careful about adjusting both sides equally... but what it to say it was running true in the first place?

Would prefer a little more poke off the line so I think I will re-do the chain and rear sprocket when the 15 tooth front sprocket lands! Starting from scratch is often the best approach when other people (or alleged mechanics) have been tinkering before you!  

I feel the lugging under 3k is a load related issue as well - since fitting a Screamin Demon pipe is has gotten a little better (and sounds awesome as well!) will be rejetting shortly when the lunchbox arrives and I will be giving the ignition advance mod a go as well - hopefully I will be able to get the best balance with jets for all RPM ranges!

[centuryghost]

The only time I'm below 3k is at idle. You need to rev it out more, the twin will like you for it 

[Toogoofy317]

So, are you riding with an aftermarket exhaust and didn't rejet? That combined with under 3k will cause the chug a chug effect. You need to rejet sooner rather than later

Mary

[redhenracing2]

Meh, I personally don't think rejetting is that important. My gs was straightpiped for the longest time, and never had any issue from it. My current bike has a full exhaust with stock jets, and runs perfectly.

The lower gearing will definitely help it out, and the ignition advance is supposed to help unlock a little torque as well.

[Twisted]

I too have installed a Screaming Demon exhaust and have not had to rejet. Bike runs fine as is.



They sound great eh?   Best when you decelerate and you get that nice snap, crackle and pop.

I always use 2nd gear for low speed corners, my bike seems to like it better when the revs are a lil higher as it does tend to lug if in the wrong gear.

[Unsane]

So, are you riding with an aftermarket exhaust and didn't rejet? That combined with under 3k will cause the chug a chug effect. You need to rejet sooner rather than later

Mary

The chug-a-chug effect actually improved slightly when the pipe was installed! But I will be experimenting with the jets once the intake goes on.

I too have installed a Screaming Demon exhaust and have not had to rejet. Bike runs fine as is.



They sound great eh?  Best when you decelerate and you get that nice snap, crackle and pop.

I always use 2nd gear for low speed corners, my bike seems to like it better when the revs are a lil higher as it does tend to lug if in the wrong gear.

Damn right they do - I have the full stainless model and with the baffle removed it sounds just as bassy as my mate's TLR with twin Yoshi pipes. I love it! And yes the overun crackling is sweet... Im sure there are flames leaping out of the pipe!

[Twisted]

Just remember to not be scared to rev your bike. GS's love it. I was a bit timid with mine when I first got it and used to lug around corners like a noob. GS500s idle @ 3k while warming up with choke so maybe you just need to drop down a gear when cornering. Like people have said. Your bike has it's own personality. It has likes and dislikes and the more you ride it the quicker you get to know them.

[mister]

3k rpm? Yep, that's lugging the engine.

Try this... when you change gears going up, change at 5k to 5.5k - for cruising around town.

When slowing down, when you hit 3k change down.

Michael